Typewriting apparatus with constantly rotating type disc



DISC

2 Sheets-Sheet 1 FIG. 2

M. RUDERFER FIG. i

FIG. 4

MG APPARATUS WITH CONSTANTLY ROTATING TYPE TYPEWRITI Filed June 10, 1960Feb. 12, 1963 DUTY/[CEMENT 116K053 1 147! MARTIN gfi z an Y ufl w-ATTORNEYS Feb. 12 1963 M. RUDERFER 3,077,256

TYPEWRITING APPARATUS WITH CONSTANTLY ROTATING TYPE DISC Filed June 10,1960 2 Sheets-Sheet 2 ums: FIG.6 6 I 6 Z 79 91 w a] I I 32 FIG.7

l l I L l INVENTOR- MARTIN RUDERFER ATTORNE 3,977,256 TYPEWRITINGAPPARATUS WITH CQNSTANTLY ROTATING TYPE DISC Martin Ruderfer, Brooklyn,N.Y., assignor to Dimensions, Incorporated Filed June 10, 1960, Ser. No.35,156 16 Claims. (Cl. 1Q7-18) This invention relates to typewritingapparatus wherein type faces are selectively brought into printingcontact with a platen and, more particularly, to a novel method andapparatus for reducing the printing contact time between the type facesand the platen and also for reducing the impact energy absorbed by theplaten. These improvements are especially advantageous in typewritingapparatus wherein the type faces are disposed about the periphery of aconstantly rotating disc which is selectively displaced into engagementwith the platen.

In a constantly rotating-disc typewriter, the quality of printing islargely determined by the time increment required for each type face tocome into and out of contact with the platen, because the longer thetype face and platen are in contact the more the rotary motion of thedisc tends to blur the printed character. There are definite practicallimits, however, in the extent to which this time increment can bereduced because as the type face is brought into contact with the platenmore rapidly the impact energy absorbed by the platen increases. As aresult of the small area of the type faces, the resultant impactstresses on the platen can exceed its yield strength, and damage theplaten severely.

This invention has as its general purpose the provision of typewritingapparatus, particularly of the constantly rotating-disc type, in whichthe type faces strike the platen and rebound therefrom in appreciablyless time than has been possible theretofore. This is achieved, however,by means which minimize the stress exerted on the platen. As aconsequence of these improvements, substantially longer life is impartedto the typewriting apparatus and, perhaps more importantly, the qualityof the printing is greatly enhanced.

Broadly stated, the invention relates to typewriting apparatus whereintype faces (which may be on a constantly rotating disc) are adapted tobe brought into printing contact with a platen by selective relativedisplacement towards the platen of a member supporting the type faces.The improvement comprises a frame and stop means mounted thereon. Thestop means are located with respect to one of the type face-supportingmember and platen to reverse the motion thereof at substantially thesame time the type face contacts the platen. The stop means are adaptedto accomplish this reversal of motion in substantially less time than itwould take for the type face to rebound from the platen alone.

In one embodiment of this apparatus, the stop means comprises magnetelements mounted on the type facesupporting member and framerespectively with surfaces of like polarity opposed to one another.Spring means are included for urging the member away from the platen.These magnet elements are adapted without colliding to reverse themotion of the arm at substantially the same time the type face contactsthe platen.

In another general embodiment, which is perhaps even more important, theimprovement resides in a frame and a stop element mounted thereon. Thisstop element is located with respect to one of the type face-supportingmember and platen to collide therewith at substantially the same timethe type face contacts the platen.

The invention further provides a method of making printing contactbetween a platen and type faces mounted on a supporting member. Thismethod comprises momentarily displacing the member toward the platen inatent printing contact therewith. Substantial further displacement ofthe member is impeded by means other than the platen at substantiallythe same time the type face strikes the platen. Thereafter, thedisplacement of the member is reversed in substantially less time thanit would take for the member to rebound from the platen alone. In oneembodiment of this method, the member is a disc which is constantlyrotated about its center. Momentarily, the disc is laterally displacedtoward the platen along a curved path having a center remote from andsubstantially coplanar with the disc. The direction of angular motion ofthe disc along this curved path is opposite to the direction of rotationthereof about its center and the tangential velocity of the type facesrelative to the center of the disc is less than the tangential velocityof the type faces relative to the center of the curved path.

Various particular embodiments of the broad inventive concept aredescribed hereinbelow, but all are character ized in that they provide amethod and means for re bounding the type face away from the platen at asubstantially faster rate than the platen could alone. This is to saythat the coefiicient of restitution of the type faces (the ratio ofoutgoing to incoming velocity) is greatly increased by relying uponauxiliary means other than the platen to rebound the type face. Theseauxiliary means reduce the printing contact time and isolate the platenfrom a substantial portion of the impact energy, with the result thatthe printed characters are more distinct and the life of the platen islengthened.

Preferred embodiments of the new apparatus are described hereinbelowwith reference to the accompanying drawings, wherein I FIG. 1 is afragmentary plan view of partly broken way typewriting apparatusembodying the invention;

FIG. 2 is a fragmentary section taken along the line 22 of FIG. 1;

FIG. 3 is a vector diagram illustrating the principle of operation ofthe new apparatus;

FIG. 4 is a displacement curve also illustrating the principle ofoperation;

FIG. 5 is a diagrammatic plan view of another embodiment of theapparatus; 1

FIG. 6 is a diagrammatic plan view of a further embodiment of theapparatus; and

FIG. 7 is a digrammatic plan view of yet another em: bodiment of theapparatus.

Referring now to FIGS. 1 and 2, the apparatus includes a rotatableplaten 10 mounted on a carriage 11 which is adapted to index the platen10 to printing position in any suitable manner. It is common practice inthe art to surface the platen 10 with a layer of rubber to permit acertain amount of penetration of the type faces during printing. Forconvenience, reference is made in the specification hereinbelow and inthe following claims to conr tact between the type faces and the platen.Actually, of

course, the type faces generally contact a sheet of paper 12 overlyingthe platen or an inking ribobn overlying the paper. It is to beunderstood, therefore, that reference to contact between the type facesand the platen includes within its meaning contact between the typefaces and the paper overlying the platen or the ribbon overlying thepaper.

Mounted adjacent the platen 10 substantially coplanar with the centerline thereof is a rotatable disc 14. A plurality of type faces 15,generally forty-two to fortyfour in number, are disposed about theperiphery of the disc 14. Upper and lower cases of these type faces maybe provided by including two rows about the periphery of the disc andincorporating the usual means for shifting to the desired row.

The disc 14 is afiixed coaxially to a first shaft 17 which is supportedby two arms 18 and 19. The arms 18 and 19 are in rotatable engagementwith the shaft 17 by means of bearings 20 and 21, respectively. Oppositethe bearing 21, the arm 19 is rotatably mounted about a second shaft 23by means of a bearing 24. The second shaft 23 is the drive shaft of anelectric motor 25 mounted on a frame 26. At the end portion of the shaft23 opposite the motor 25 is a journal bearing 27 also mounted on theframe 26. Rotation is imparted from the second shaft 23 to the firstshaft 17 by a pinion 29 on the former which meshes with a larger gear 30on the latter.

At the outer end of the second shaft 23 is an electro magnetic orelectrostrictive clutch 32 or the like which includes a driving element33 and a driven element 34. Normally, the clutch 32 is de-energized sothat rotation is not imparted from the shaft 23 to the driven element34. However, when the clutch is energized, the driven element 34 rotateswith the driving element 33 and with the shaft 23. Affixecl to thedriven element 34 of the clutch 32 is the end of the disc-supporting arm18 opposite the end thereof which is in rotatable engagement with thefirst shaft 17.

By this construction, the arm 18 is adapted to pivot about the shaft 23whenever the clutch 32 is momentarily energized. This causes the disc 14to be displaced momentarily in a counter-clockwise direction as shown inFIG. 1. One of the type faces 15 on the periphery of the disc is therebybrought into printing contact with the platen 10. Selective actuation ofthe clutch 32 in this manner may be accomplished in any suitable manner,for example by the circuitry described in my US. Patent No. 2,675,108.Thus, a commutator 36 may be in engagement with a brush 37 on the end ofthe first shaft '17- so that at the proper moment the clutch 32 isenergized when the appropriate key is struck on a keyboard 33 (shown indotted lines in FIG. 2).

Since the disc 14 is constantly rotating when brought into printingcontact with the platen It as described, it is necessary to keep theprinting contact time to a minimum in order to prevent blurring of theprinted character. At the same time, the relatively inelastic rubberplaten must not be damaged by the impact energy of the disc assembly.Thus, in accordance with the invention, the arm 13 which actuates thedisc 14 during printing normally rests against an abutting element 40attached to the frame. Also, a tension spring 41 interconnects the frameand the arm 18 to urge the arm against the abutting element 4% Thesemembers establish the normal position of the disc 14 relative to theplaten Spaced between the outer end of the arm 18 and the platen 13 is astop element 43 against which the portion 44- (FIG. 1) of the arm 13collides substantially at the same time the particular type face engagesthe platen 10'. The stop element 43 may be provided with a centralcut-out portion 46 as shown in FIG. 1 to decrease its stiffness; ingeneral the stop element 43 is considerably more elastic than the platen1ft.

When the clutch 32 is energized momentarily, the arm 18 pivots in acounter-clockwise direction as seen in FIG. 1. At all times, of course,the disc 14 is rotating in a clockwise direction as shown in FIG. 1because of the gear and pinion drive between the shafts 23 and 17. Also,the arm 18 is pivoted by the clutch 32 at a greater angular velocitythan that of the disc 14 with respect to its shaft 17 because the pinion29 is substantially smaller than the gear 30. Therefore, the particulartype face 15 which engages the platen 10 has velocity components asshown in the vector diagram of FIG. 3.

v The vector V represents the tangential velocity of the type face 15relative to the pivot point of the arm 13 and is thus perpendicular to aline joining the center line of the shaft 23 with the point of contactof the type face on the platen. The vector V represents the tangentialvelocity of the type face relative to the center line of the shaft 1'7and is thus parallel to the surface of the platen 10. These twocomponents V and V are added to give a resultant vector V which is theactual incoming velocity of the type face relative to the platen 10. Asis apparent from the vector diagram of FIG. 3, V can be perpendicular tothe platen 10 if the magnitude and direction of V and V are properlychosen. A perpendicular approach of the type face relative to the platen10 is most advantageous, of course, because the type face then does notwipe across the platen and thereby blur the printed character and theplace of impact of the type face on the platen parallel to the centerline of the platen is not affected by the number of sheets overlying theplaten. The magnitude and direction of V and V may be varied to give theproper resultant velocity V,. by suitable selection of the gear 23 andpinion 30, the length of the arm 13, and the angle between the point ofcontact with platen and the line joining the center of shafts 17 and 23.

As soon as or just before the particular type face 15 engages the platen10, the surface 44 on the arm 18 also collides with the stop element 43as described. Because the stop element 43 is considerably more elasticthan the platen 10, it is the stop element which principally impedessubstantial further motion of the type face and shortly thereafterreverses the direction of motion of the arm 18. This is to say that thedisc assembly strikes both the stop element 43 and the platen 10 but isrebounded only by the stop element. Because of the high elasticity ofthe stop element 43, the coefficient of restitution of the disc assembly(i.e. the ratio of outgoing to incoming velocity) is close to unitySince the platen 10 is relatively inelastic, it returns to normalposition more slowly and thus lags behind the type face during therebound.

The velocity of the type face during the rebound. is also shown in thevector diagram of FIG. 3. Under rebound conditions, the arm 18 ispivoting clockwise as shown in FIG. 1 so that the type face has atangenital velocity relative to the point of the pivot of the arm 18represented by the vector V,,. The tangential velocity of the type facerelative to the center line of the shaft 17 is, of course, still Vduring the rebound. The resultant velocity of V,,, and V is representedby the vector V which is of considerably greater magnitude than theresultant incoming velocity V;..

The effect these velocities have on the movement of the type facerelative to the platen is illustrated by the curve shown in FIG. 4.Displacement of the type face into the platen is plotted as the ordinateand displacement of: the type face across the platen is plotted as theabscissa. The type face first contacts the platen at the point 0 on thecurve while moving at the velocity V,. At the same time, of course, thearm 18 also contacts the stop element 43. Then the type face penetratesinto the platen a distance y while moving across the platen a distance xto the point p on the curve. (The distance O-x is to be kept to aminimum to prevent blurring during entry of the type face into theplaten.) Upon reaching the point p, the motion of the type face isreversed by the stop element 43 and the disc assembly rebound'therefromat a velocity which reaches the magnitude and direction of V at thepoint x where the type face passes the surface at which it originallycontacted the platen. However, it is important to note that while movingfrom the point p (the maximum point of penetration) to the point x thetype face is not in contact with the platen 10 because the relativelyinelastic platen 1i lags behind the type face during the rebound.

Therefore, as a result of incorporating stop element 43 in theapparatus, the contact time between the type face and the platen is onlythe time required for the type face to move the distance O-p along thecurve. This is less than half the time required if the stop element werenot used to effect the rebound and the type face stayed in contact withthe platen during the rebound (from p to x on the curve). Hence, thestop element 43 has the ability to minimize printing contact time andthus improve the quality of the printed characters.

In addition, the impact of the disc assembly is taken up primarily bythe stop element 43 rather than by the platen so that this reduction incontact time does not unduly stress the platen. Yet there is nopossibility that the stop element 43 will itself be damaged by theimpact of the disc assembly because the area of contact at the portion44 of the arm 18 can be sufficiently extensive to reduce the resultingstress well below maximum limits.

It is also important to note that when the disc 14 rotates in adirection opposite to the displacement of the arm 18 during printing,the incoming velocity V of the type face is closest to perpendicular.This condition is also made possible by rotating the disc 14 at a lesserangular velocity than that of the arm 18 during printing such that thevelocity V of the type face relative to the center line of the disc isless than the velocity V of the type face relative to the point of pivotof the arm 13. If the motion of the type face does not have a componentV opposite to V then the incoming portion of the curve 0p would belengthened until the curve is symmetrical. Since this portion 0prepresents contact between type face and platen, such lengthening causesan increase in blurring. Consequently, the retrograde rotation of thedisc contributes further to the quality of the printing.

In FIG. 5, a modification of the stop element is shown in detail. An arm50 is adapted to be periodically pivoted about a shaft 51 as in thepreviously described structure. The arm 50 rotatably supports a typefacebearing disc 52 (shown in dotted lines) which normally is spacedfrom a platen 53 (also shown in dotted lines). A tension spring 54 urgesthe arm 50 against an abutting element 55.

As in the previous embodiment, a portion 56 of the arm 54 is adapted tocollide with a stop element 58 mounted on a frame 59 at substantiallythe same time the disc 52 comes into printing contact with the platen53. However, means are provided for varying the time of contact betweenthe arm 50 and stop element 58 relative to the time of contact betweenthe disc 52 and platen 53 and also for varying the elasticity of thestop element 58. Thus, the stop element is made up of a pair of slightlyresilient bars 60 and 61 which are placed apart side-by-side and rigidlyinterconnected at one end portion 62. An adjustment screw 63interconnects the opposite ends of the bars 60 and 61. The bars 61 fitswithin a slot in the frame 59 and can be aflixed at various positions inthe slot by a screw 64. The bar 60 is disposed such that it is struckintermediate its ends by the portion 56 r f the arm 50.

By turning the adjustment screw 63, the bar 66 may be deflected towardor away from the bar 61 so that the arm 59 collides with the bar 60 atdifferent points in time relative to the collision between the disc 52and platen 53. This permits variation in the depth of penetration of thetype face into the platen and is useful in typing different numbers ofcopies. By locking the bar 61 at different positions in the slot in theframe 59 (by means of the screw 64) various points of collision may bepresented to the portion 56 of the arm. If the stop element is moved tothe left as shown in FIG. 5, the elasticity of the stop element (or,more particularly of the bar 60*) is decreased because the portion 56 ofthe arm 50 strikes the bar 60 at a point further removed from the rigidconnecting portion 62. Conversely, if the stop element is moved to theright as shown in FIG. 5, the portion 56 of the arm 50 strikes the bar60 at a point closer to the connecting portion 62 and thus theelasticity is increased. This adjustment permits even closer control tobe maintained over the depth of penetration of the type face into theplaten.

Referring now to the modification shown in FIG. 6, an arm 65 is againadapted to be pivoted about a shaft 66 to displace a disc 67 (shown indotted lines) toward a platen 68 (also shown in dotted lines). Moreover,the arm 65 is urged toward a frame 70 by means of a tension spring 71such that the arm rests against an abutting element 72.

A stop element 73 is provided in this modification which difiers fromthose previously discussed in that no collision occurs between it andthe arm 65. Magnet elements 75 and 76 are mounted on the arm 65 andframe 70, respec tively, with surfaces of like polarity opposed to oneanother. The strength of these magnet elements 75 and 76 is such thatthe force of repulsion between the opposed surfaces is sufficient toreverse the motion of the arm 65, substantially as elastically as in theprevious embodiments, at the same time the type face strikes the platen.This structure is characterized in that both the platen and the stopelement are isolated from impact. In many instances, the resultingreduction in vibrations in the apparatus frame may be quiteadvantageous.

The apparatus shown in FIG. 7 differs from the embodiments of FIGS. 1and 2 not in the construction of the stop element but rather in themechanism used for selectively displacing the disc assembly towards theplaten. Again, a disc 7%; and platen 79 (both shown in dotted lines) arespaced apart and the disc is rotatably mounted on the end of arm 89. Thearm 80 is pivoted about a shaft 81 and, by any suitable means, constantrotation is imparted to a shaft 82 supporting the disc 78.

Supported on a frame 84 adjacent the arm 80 is an electromagnet 85 whichis adapted to be normally energized by a coil 86. Through suitablecircuitry, the coil 85 may be de-energized by the various keys on akeyboard 87 when the appropriate type face on the disc 78 is approachingthe platen. A permanent magnet may be used in place of the core of theelectromagnet S5 and circuitry provided to de-energize the magnet when asuitable 'current is passed through the coil 86. The poles of theelectromagnet 85 are spaced a very slight distance apart in the normalposition of the apparatus from an armature 89 of magentic materialafiixed to the arm 80. A spring 90 interconnects the frame 84 and theend of the arm 80 and a stop element 91 (of any of the types describedpreviously) is mounted on the frame to reverse the motion of the arm 80substantially at the same time the type face contacts the platen 79'.

In this apparatus, the spring 90 is in compressed condition when the arm80 is in normal position spaced from the stop element 91. Theelectromagent 85 is normally energized and this urges the arm 80 againstthe force of the spring 90 to compress it. Upon selectivede-energization of the electromagnetic coil 86, the force of attractionbetween the electrom-agnet 85 and the armature 89' on the arm 80 issuddenly eliminated with the result that the spring 99 expands to drivethe arm 80 rapidly towards the stop element 91. Before the arm 80strikes the stop element 91, the spring 90 may pass from compression totension but the momentum of the disc assembly carries the arm 80 furtherinto contact with the stop element 91 at the same time the type facestrikes the platen 79. In rebounding from the stop element 91, the arm80 maybe assisted by the spring 9% (which may now be in tension) so thatit withdraws very rapidly. Again, the momentum of the disc assemblycauses the arm 80 to compress the spring 90 once again and before themomentum of the assembly is expended the arm 80 is recaptured by theelectromagnet 85 in the position shown in FIG. 7.

One of the major advantages of this spring-propelled means fordisplacing the disc assembly is that the amplitude of the spring isindependent of its period. Thus, variations in the starting position ofthe arm 81) (because of wear, dirt, and so on) do not affect the timerequired for displacement into printing contact.

The stop means 91 is of particular advantage'in this embodiment becauseit rebounds the disc assembly substantially to its starting position foreasy recapture of the disc assembly by the magnet 85'. Hence, the magnet85 need not be impractically large.

It is quite obvious that various modifications can be made in the basicinventive concept described herein without departing from the scope ofthe invention. For example, the platen may be displaced into contactwith the disc, rather than the converse described herein. In that case,the stop element would impede and reverse the motion of the platenrather than the disc assembly. There are, of course, many othersubstitutions which may be made in the new method and apparatus whichare understood to be fully covered by the following claims.

A further variation within the scope of the invention is to support theconstantly rotating disc on the movable end of a shaft having an elbowintermediate its ends. The arm is then adapted to pivot thedisc-supporting end of this shaft toward the platen during each printingoperation. In such case, the elbow is in the form of a universal jointto transmit constant rotation from the shaft to the disc. The principlesof operation otherwise remain substantially the same since the arm stilldisplaces the shaft laterally but in a pivotal manner rather than a fulllateral translation as described previously.

I claim:

1. Typewriting apparatus comprising a frame, a platen mounted on saidframe, a rotatable disc adjacent said platen, a plurality of type facesdisposed about the periphery of said disc, a first shaft afiixedcoaxially to said disc, a second shaft rotatably mounted on said frameand extending alongside said first shaft, means for constantly rotatingboth of said shafts, a selectively engageable clutch on said secondshaft comprising driving and driven elements, an arm extending rigidlyfrom said driven element and being in rotatable engagement with saidfirst shaft, means for selectively momentarily engaging said clutch topivot said arm and being one of the type faces into printing contactwith said platen, and stop means on said frame for reversing the motionof said arm at substantially the same time the type face contacts saidplaten, said stop means being adapted to accomplish this reversal ofmotion in substantially less time than it would take for said type faceto rebound from the platen alone.

2. Typewriting apparatus comprising a frame, a platen mounted on saidframe, a rotatable disc adjacent said platen, a plurality of type facesdisposed about the periphery of said disc, a first shaft affixedcoaxially to said disc, a second shaft rotatably mounted on said frameand extending parallel alongside said first shaft, a motor on said framefor constantly rotating said second shaft, transmission means forinterconnecting said shafts for rotating said first shaft, a selectivelyengageable electrically operative clutch on said second shaft comprisingdriving and driven elements, an arm extending rigidly from said drivenelement and being in rotatable engagement with said first shaft,commutator means associated with said first shaft for selectivelymomentarily engaging said clutch to pivot said arm and said disc towardsaid platen to bring one of the type faces into printing contact withsaid platen, and stop means on said frame for reversing the motion ofsaid arm at substantially the same time the type face contacts saidplaten, said stop means being adapted to accomplish this reversal ofmotion in substantially less time than it would take for said type faceto rebound from the platen alone.

3. Apparatus according to claim 1 wherein said stop means comprisesmagnet elements mounted on said arm and frame respectively with surfacesof like polarity opposed to one another, and means for urging said armaway from said platen, said magnet elements being adapted withoutcolliding to reverse the motion of said arm at substantially the sametime the type face contacts the platen.

4. Typewriting apparatus comprising a frame, a platen mounted on saidframe, a rotatable disc adjacent said platen, a. plurality of type facesdisposed about the pcriphery of said disc, a first shaft aflixedcoaxially to said disc, a second shaft rotatably mounted on said frameand extending parallel alongside said first shaft, a motor on said framefor constantly rotating said second shaft, gear and pinion meansinterconnecting said shafts for rotating said first shaft, a selectivelyenageable electrically operative clutch on said second shaft comprisingdriving and driven elements, an arm extending rigidly from said drivenelement and being in rotatable engage ment with said shaft, commutatormeans for momentarily engaging said clutch to displace said arm and saiddisc toward said platen to bring one of the type faces into printingcontact with said platen, and a stop element mounted on said frame, saidarm being adapted to col lide with said stop element at substantiallythe same time said type face contacts said platen, said stop elementbeing substantially more elastic than said platen.

5. Apparatus according to claim 4 wherein said arm is pivoted towardsaid platen in a direction opposite to the direction of rotation of saiddisc.

6. Apparatus according to claim 5 wherein the tangential velocity of thetype face contacting said platen relative to the center of said disc isless than the tangential velocity of that type face relative to thepoint of pivot of said arm.

7. Apparatus according to claim 4 wherein said stop element includesadjustment means for varying the depth of penetration of the type faceinto said platen.

8. Apparatus according to claim 7 wherein said adjustment meanscomprises a pair of slightly resilient bars spaced apart side-by-sideand cojoined at one end, said arm being adapted to collide with one ofsaid bars between the ends thereof, an adjustment screw interconnectingthe opposite ends of said bars for varying the space between them, and asliclable mount for displacing said stop element so that said armcollides at various points relative to the cojoined ends of said bar.

9. In typewriting apparatus wherein type faces on a constantly rotatingdisc are adapted to be brought into printing contact with a platen byselective relative displacement toward said platen of a membersupporting said disc, the improvement which comprises a frame and stopmeans mounted thereof, said stop means comprising magnet elementsmounted on said member and frame respectively with surfaces of likepolarity opposed to one another, and means for urging said member awayfrom said platen, said magnet elements being adapted without collidingto reverse the motion of said member at substantially the same time thetype face contacts the platen, said stop means being adapted toaccomplish this reversal of motion in substantially less time than itwould take for the type face to rebound from the platen alone.

10. Typewriting apparatus comprising a frame; a platen mounted on saidframe; a rotatable disc adjacent said platen; a plurality of type facesdisposed about the periphery of said disc; an arm pivoted on said frameand supporting said rotatable disc; means for selectively dis placingsaid arm toward said platen to bring one of the type faces into printingcontact with said platen; and a stop element mounted on said frame, saidarm being adapted to collide with said stop element at substantially thesame time the type face contacts said platen, said stop element beingsubstantially more elastic than said platen; said means for displacingsaid arm comprising an armature of magnetic material on one of saidframe and said arm remote from the pivot point thereof, a selectivelydeenergizable magnet opposed to said armature on the other of said frameand said arm remote from the pivot point thereof, and a spring normallyin compression interconnecting said arm and said frame, whereby saidspring urges said arm into contact with said stop element when saidmagnet is momentarily deenergized and said magnet regrips said arm aftersaid arm rebounds from said stop element.

11. Typewriting apparatus comprising a frame, a

platen mounted on said frame, a rotatable disc adjacent said platen, aplurality of type faces disposed about the periphery of said disc, afirst shaft afiixed coaxially to said disc, a second shaft rotatablymounted on said frame and extending substantially alongside said firstshaft, means for constantly rotating both of said shafts, a selectivelyengageable clutch on said second shaft comprising driving and drivenelements, an arm extending rigidly from said driven element and being inrotatable engagement with said first shaft, and means for selectivelymomentarily engaging said clutch to pivot said arm and bring one of thetype faces into printing contact with said platen.

12. Typewriting apparatus comprising a frame, a platen mounted on saidframe, a rotatable disc adjacent said platen, a plurality of type facesdisposed about the periphery of said disc, a first shaft affixedcoaxially to said disc, at second shaft rotatably mounted on said frameand extending parallel alongside said first shaft, a motor on said framefor constantly rotating said second shaft, transmission means forinterconnecting said shafts for rotating said first shaft, a selectivelyengageable electrically operative clutch on said second shaft comprisingdriving and driven elements, an arm extending rigidly from said drivenelement and being in rotatable engagement with said first shaft, andcommutator means associated with said first shaft for selectivelymomentarily engaging said clutch to pivot said arm and said disc towardsaid platen to bring one of the type faces into printing contact withsaid platen.

13. Typewriting apparatus comprising a frame, a platen mounted on saidframe, a rotatable disc adjacent said platen, a plurality of type facesdisposed about the periphery of said disc, a first shaft affixedcoaxially to said disc, a second shaft rotatably mounted on said frameand extending substantially alongside said first shaft, means forconstantly rotating both of said shafts, a selectively engageable clutchon said second shaft comprising driving and driven elements, an armextending from said driven element and being in rotatable engagementwith said first shaft, and means for selectively displacing said armtoward said platen in a direction opposite to the direction of rotationof said disc to bring one of the type faces into printing contact withsaid platen.

14. Typewriting apparatus comprising a frame, a platen mounted on saidframe, a rotatable disc adjacent said platen, a plurality of type facesdisposed about the periphery of said disc, a first shaft afiixedcoaxially to said disc, a second shaft rotatably mounted on said frameand extending substantially alongside said first shaft, means forconstantly rotating both of said shafts, a se lectively engageableclutch on said second shaft comprising driving and driven elements, anarm extending from said driven element and being in rotatable engagementWith said first shaft, means for selectively momentarily engaging saidclutch to displace said arm and said disc toward said platen in adirection opposite to the direction of rotation of said disc to bringone of the type faces into printing contact with said platen, and stopmeans mounted on said frame, said stop means being adapted to reversethe motion of said arm at substantially the same time the type facecontacts the platen, said stop means being adapted to accomplish thisreversal of motion in substantially less time than it would take for thetype face to rebound from the platen alone.

15. Typewriting apparatus comprising a frame, a platen mounted on saidframe; a rotatable disc adjacent said platen; a plurality of type facesdisposed about the periphery of said disc; an arm pivoted on said frameand supporting said rotatable disc; means for selectively displacingsaid arm toward said platen in a direction opposite to the direction ofrotation of the disc to bring one of the type faces into printingcontact with said platen; stop means mounted on said frame, said stepmeans being adapted to reverse the motion of said arm at substantiallythe same time the type face contacts the platen, said stop means beingadapted to accomplish this reversal of motion in substantially less timethan it would take for the type face to rebound from the platen alone;said means for selectively displacing said arm comprising an armature ofmagnetic material on one of said frame and said arm remote from thepivot point thereof, a selectively deenergizable magnet opposed to saidarmature on the other of said frame and said arm remote from the pivotpoint thereof, and a spring normally in compression interconnecting saidarm and said frame, whereby said spring urges said arm toward said stopmeans when said magnet is momentarily deenergized and said magnetregrips said arm after said arm returns from said stop means.

16. Typewriting apparatus comprising a frame; a platen mounted on saidframe; a constantly rotatable disc adjacent said platen; a plurality oftype faces disposed about the periphery of said disc; an arm pivoted onsaid frame and supporting said rotatable disc; means for selectivelydisplacing said arm toward said platen in a direction opposite to thedirection of rotation of said disc to bring one of the type faces intoprinting contact with said platen comprising an armature of magneticmaterial on one of said frame and said arm remote from the pivot pointthereof, a selectively deenergizable magnet opposed to said armature onthe other of said frame and said arm remote from the pivot pointthereof, and a spring normally in compression interconnecting said armand said frame; and stop means mounted on said frame adapted to reversethe motion of said arm at substantially the same time the type facecontacts the platen, said stop means being adapted to accomplish thisreversal of motion in substantially less time than it would take for thetype face to rebound from the platen alone; whereby said spring urgessaid arm toward said stop means when said magnet is momentarilydeenergized and upon being immediately reenergized said magnet regripssaid arm after said arm returns from said stop means.

References Cited in the file of this patent UNITED STATES PATENTS1,458,125 Barney June 12, 1923 1,553,765 Fischer Sept. 15, 19252,328,638 Fuller et al. Sept. 7, 1943 2,675,108 Ruderfer Apr. 13, 19542,770,188 Nolan Nov. 13, 1956 2,790,381 Miossec et al. Apr. 30, 19572,799,221 Olivetti July 16, 1957 2,940,385 House June 14, 1960 2,981,178Bender Apr. 25, 1961 UNITED STATES PATENT OFFICE GERTIFICATE OFCORRECTION Patent Noe 5x077 256 February 12 1963 Martin Ruderfer It ishereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 2 line 4,5 for "digrammatic read diagrammatic line 57, for"ribobn read ribbon column 5 line 63 for "left" read right line 68 for"right" read left column 7 line 36 for "being" read bring column 8, line10 before "shaft" insert first Signed and sealed this 10th day ofSeptember 1963.,

(SEAL) Attest:

ERNEST w. SWIDER DAVID L. ADD Attesting Officer Commissioner of Patents

1. TYPEWRITING APPARATUS COMPRISING A FRAME, A PLATEN MOUNTED ON SAIDFRAME, A ROTATABLE DISC ADJACENT SAID PLATEN, A PLURALITY OF TYPE FACESDISPOSED ABOUT THE PERIPHERY OF SAID DISC, A FIRST SHAFT AFFIXEDCOAXIALLY TO SAID DISC, A SECOND SHAFT ROTATABLY MOUNTED ON SAID FRAMEAND EXTENDING ALONGSIDE SAID FIRST SHAFT, MEANS FOR CONSTANTLY ROTATINGBOTH OF SAID SHAFTS, A SELECTIVELY ENGAGEABLE CLUTCH ON SAID SECONDSHAFT COMPRISING DRIVING AND DRIVEN ELEMENTS, AN ARM EXTENDING RIGIDLYFROM SAID DRIVEN ELEMENT AND BEING IN ROTATABLE ENGAGEMENT WITH SAIDFIRST SHAFT, MEANS FOR SELECTIVELY MOMENTARILY ENGAGING SAID CLUTCH TOPIVOT SAID ARM AND BEING ONE OF THE TYPE FACES INTO PRINTING CONTACTWITH SAID PLATEN, AND STOP MEANS ON SAID FRAME FOR REVERSING THE MOTIONOF SAID ARM AT SUBSTANTIALLY THE SAME TIME THE TYPE FACE CONTACTS SAIDPLATEN, SAID STOP MEANS BEING ADAPTED TO ACCOMPLISH THIS REVERSAL OFMOTION IN SUBSTANTIALLY LESS TIME THAN IT WOULD TAKE FOR SAID TYPE FACETO REBOUND FROM THE PLATEN ALONE.